1. Field of the Invention
This invention relates to propellant charge compositions containing as the propellant a nitrocellulose propellant. More particularly, this invention relates to propellant charge compositions whose activity is independent of temperature. This invention further relates to such propellant charge compositions combined with other propellant charge compositions.
2. Discussion of the Prior Art
Nitrocellulose-containing propellant charges have long been known. In the unmodified state they are known as "green powder". Generally, they burn in a ballistic bomb test producing a sharp pressure peak which is followed by a sharp and rapid drop of the pressure. The sharp pressure peak results in a failure to convert the total energy into kinetic energy as desired, some of the energy being lost in the form of static energy. The leveling of the pressure peak and the spreading out of the maximum pressure over a longer period, therefore, produces an improvement of the efficiency of the powder. A number of methods have been proposed for the modification of the propellant charge powder in order to level this undesirably sharp pressure peak and to provide a longer sustenance of the pressure.
Thus it is known to mix plasticizers or phlegmatizers with the propellant charge powders in order to flatten the pressure peak. Such substances are, for example, camphor, urea derivatives known as centralites, or esters of dibasic organic dicarboxylic acids, such as, for example, the ethyl, hexyl or octyl esters of the phthalic acids. These substances are deposited in the surface of the powder with the aid of solvents which swell the surface of the powder (cf. German "Offenlegungsschrift" No. 2,351,778, for example). They are thus within the uppermost stratum of the powder grains in a more or less thick layer. By this procedure it is possible to diminish the pressure peak and achieve a better pressure characteristic than in the case of green powder. The results achieved, however, are not satisfactory, since not only is the drop in pressure, as measured in the ballistic bomb, still too fast, but also the pressure characteristic is temperature-related.
The temperature-dependence of the powder reveals itself in the ballistic bomb in the fact that, in the burning both at low temperatures (-50.degree. C) and at room temperature, or at +50.degree. C, the dynamic liveliness (pressure change per unit of time, with respect to the sum of the pressure at the moment and the maximum pressure) is directly proportional to the temperature, i.e., the higher the temperature the greater is the liveliness measured in the ballistic bomb.
It is an object of this invention, therefore, to provide a propellant charge composition which during burning in a ballistic bomb test shows a dynamic liveliness which is independent of temperature. It is a further object of this invention, therefore, to provide a propellant charge powder which in burning produces virtually no sharp pressure peak and in which the gas pressure which develops is sustained over an extended period of time.